Failure of Success Criterion 4.1.1 due to incorrect use of start and end tags or attribute markup

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.2 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.2.


Markup languages: HTML, XHTML, and other SGML or XML-based technologies.

This technique relates to Success Criterion 4.1.1: Parsing (Failure).


The objective of this failure is to identify examples of markup errors in element tags that could cause assistive technology to be unable to generate a satisfactory model of the page. Different user agents may implement different heuristics to recover from errors, resulting in inconsistent presentations of the page between user agents.

Some common types of problems with start and end tags that lead to this failure condition (though this is not an exhaustive list):


Example 1: Missing angle brackets in XHTML

The following code fails because the opening tag is missing an angle bracket, and the intended boundary of the tag is unclear.

<p This is a paragraph</p>

Example 2: Missing slash on closing tag in XHTML

The following code fails because the closing tag is missing the slash, making it look like it is in fact another opening tag.

<p>This is a paragraph<p>

Example 3: Unbalanced attribute quoting

The following code fails because the attribute value is missing the closing quote, which makes the boundary of the attribute-value pair unclear.

<input title="name type="text">

Example 4: Lack of whitespace between attributes

The following code fails because the there is not whitespace between attributes, which makes the boundary between attribute-value pairs unclear.

<input title="name"type="text">

Example 5: Unquoted attribute with whitespace value

The following code fails because an attribute value is not quoted and contains whitespace, which makes the boundary of the attribute-value pair unclear.

<input title=Enter name here type=text>

Example 6: Missing end tags in XHTML

The following code fails because the closing tag of the first paragraph is missing, making it unclear whether the second paragraph is a child or sibling of the first.

<p>This is a paragraph
<p>This is another paragraph</p>



  1. Check the source code of pages implemented in markup languages.
  2. Check whether any opening tags, closing tags or attributes are malformed.

Expected Results

  • If check #2 is true, then the failure condition applies and the content does not meet this Success Criterion.